Process for the preparation of carbodiimide-isocyanurate foams

ABSTRACT

Rigid cellular foam compositions characterized by carbodiimide and isocyanurate linkages are prepared by catalytically condensing an organic polyisocyanate in the presence of a catalytically sufficient amount of a co-catalyst system of furfuryl alcohol and a tertiary amine trimerization catalyst.

United States Patent [1 1 Narayan et a].

PROCESS FOR THE PREPARATION OF CARBODIIMIDE-ISOCYANURATE FOAMS Inventors: Thirumurti L. Narayan, Riverview;

Moses Cenker, Trenton, both of NJ.

BASF Wyandotte Corporation, Wyandotte, Mich.

Filed: Dec. 21, 1973 Appi. No.: 427,035

Assignee:

U.S. CL. 260/25 AW; 260/2.5 AC; 260/25 BF Int. Cl C08g 22/44; C08g 33/04 Field of Search... 260/25 AW, 2.5 BF, 2.5-AC

References Cited- UNITED STATES PATENTS 2/1965 Beitchman 260/25 AW 51 July 15,1975

3,657,161 4/1972 Bernard 260/25 BF Primary ExaminerD0nald E. Czaja Assistant Examiner--C. Warren Ivy Attorney, Agent, or Firm-Joseph D. Michaels; Bernhard R. Swick; Robert E. Dunn 8 Claims, No Drawings PROCESS FOR THE PREPARATION OF CARBODIMID E-ISOCYANURATE FOAMS BACKGROUND OF THE INVENTION 1. Field of The Invention The present invention relates to a novel catalyst systern for the preparation of cellular foams characterized by carbodiimide and isocyanurate linkages. More particularly, the invention relates to the use of a cocatalyst system of furfuryl alcohol and a tertiary amine in the preparation of cellular foams characterized by carbodiimide and isocyanurate linkages.

2. Prior Art The preparation of foams containing carbodiimide linkages is well known in the art. Generally, the foams are prepared by condensing an organic polyisocyanate with a catalyst which promotes carbodiimide linkages, optionally in the presence of a blowing agent. Representative of such techings are the disclosures found in U.S. Pat. Nos. 2,941,966 and 3,645,923. The prior art also teaches that foams containing both carbodiimide and isocyanurate linkages can be prepared by condensing an organic polyisocyanate with a catalyst which promotes both carbodiimide and isocyanurate linkages or with a co-catalyst system, one catalyst promoting carboiimide linkages and one catalyst promoting isocyanurate linkages. Representative of such teachings are the disclosure found in U.S. Pat. Nos. 3,645,923; 3,657,161; 3,717,596; 3,723,366, and 3,746,709.

SUMMARY OF THE INVENTION The present invention relates to an improved process for the preparation of carbodiimide-isocyanurate foams employing a catalytically sufficient amount of furfuryl alcohol and a tertiary amine trimerization catalyst. It was surprising and unexpected to find that the use of a co-catalyst system of furfuryl alcohol and a tertiary amine provides for foams characterized by carbodiimide linkages since heretofore catalysts such as striazines and phospholene oxides were employed for this purpose.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the present invention, rigid cellular foams are prepared by the catalytic condensation of an organic polyisocyanate in the presence of a catalytically sufficient amount of furfuryl alcohol and a tertiary amine trimerization catalyst as hereinafter defined. The products which are produced in accordance herewith are rigid cellular foam plastics containing carbodiimide linkages and isocyanurate linkages. It is the carbodiimide linkages whose formation provides the carbon dioxide blowing agent and which, together with the isocyanurate linkages, imparts the excellent flame properties to the products.

Tertiary amine trimerization catalysts which are employed in the present invention include 1,3,5-tris(N,N- dialkylaminoalkyl)-s-hexahydrotriazines; the alkylene oxide and water adducts of l,3,5-tris(N,N- dialkylaminoalkyl)-s-hexahydrotriazines; 2,4,6-tris(- dimethylaminomethyl)phenol; o-, por a mixture of oand p-dimethylaminomethylphenol and triethylene diamine or the alkylene oxide and water adducts thereof. These compounds are well known in the art, as is their use as catalysts which promote isocyanurate linkages.

2 1,3 ,5-Tris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine compounds have heretofore been described as useful co-catalysts or isocyanate trimerization catalysts. See U.S. Pat. No. 3,723,366, the disclosure of which is hereby incorporated by reference. Preferred within this group of hexahydrotriazine compounds is l ,3 ,5-tris( N,N-dimethylaminopropyl )-s-hexahydrotriazine.

The alkylene oxide and water adducts of a 1,3,5-

tris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine is presumably a quaternary ammonium hydroxide. These compounds are generally prepared by reacting equimolar amounts of the hexahydrotriazine, alkylene oxide and water at a temperature of from about 10C. to C. for a period of from about 5 minutes to 2 hours. Preferred within this group of compounds is the propylene oxide and water adduct of l,3,5-tris(N,N- dimethylaminopropyl)-s-hexahydrotriazine. See U.S. Pat. Nos. 3,746,709 and 3,766,103, the disclosures of which are hereby incorporated by reference.

2,4,6-Tris(dimethylaminomethyl)phenol as well as o-, pand a mixture of oand p- (dimethylaminomethyl)phenol are known compounds which are commercially available products sold by Rohm & Haas under the trade names DMP-30 and DMP-lO. Triethylenediamine and the alkylene oxide and water adducts thereof are also well-known compounds commercially available under the trade name Dabco.

The amount of trimerization catalyst which may be employed in the present invention is generally from 0.1 part to 20 parts of catalyst per parts of organic polyisocyanate. The amount of furfuryl alcohol which is employed is generally from 0.1 part to 10 parts per 100 parts of organic polyisocyanate.

The organic polyisocyanate used in the preparation of the foams in accordance with the present invention corresponds to the formula:

wherein R" is a polyvalent organic radical which is either aliphatic, aralkyl, alkaryl, aromatic or mixtures thereof, and z is an integer which corresponds to the valence of R" and is at least two. Representative of the organic polyisocyanates contemplated herein includes, for example, the aromatic diisocyanates, such as 2,4- toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate, crude toluene diisocyanate, methylene diphenyl diisocyanate, crude methylene diphenyl diisocyanate and the like; the aromatic triisocyanates such as 4,4',4"- triphenylmethane triisocyanate, 2,4,6-toluene triisocyanates; the aromatic tetraisocyanates, such as 4,4- dimethyldiphenylmethane-2,2 -5 ,5 -tetraisocyanate, and the like; arylalkyl polyisocyanates, such as xylylene diisocyanate; aliphatic polyisocyanates, such as hexamethylene-l,6-diisocyanate, lysine diisocyanate methylester and the like; and mixtures thereof. Other organic polyisocyanates include polymethylene polyphenylisocyanate, hydrogenated methylene diphenylisocyanate, m-phenylene diisocyanate, naphthylene-l ,5- diisocyanate, l-methoxyphenyl-2,4-diisocyanate, 4,4- biphenylene diisocyanate, 3 ,3 '-dimethoxy-4,4 biphenyl diisocyanate, 3,3-dimethyl-4,4-biphenyl diisocyanate, and 3 ,3 -dimethyldiphenylmethane-4,4 diisocyanate.

These polyisocyanates are prepared by conventional methods known in the art such as the phosgenation of the corresponding organic amine.

Still another class of organic polyisocyanates contemplated for use herein are the so-called quasiprepolymers. Three quasi-prepolymers are prepared by reacting an excess of organic polyisocyanate or mixtures thereof with a minor amount of an active hydrogen containing compound as determined by the wellknown Zerewitinoff test, as described by Kohler in Journal Of The American Chemical Society, 49, 3181 (1927). These compounds and their methods of preparation are well known in the art. The use of any one specific active hydrogen compound is not critical hereto, rather any such compound can be employed herein.

Suitable active hydrogen-containing groups as determined by the Zerewitinoff method which are reactive with an isocyanate group include OH, NH, -COOl-l, and SH. Examples of suitable types of organic compounds containing at least two active hydrogen-containing groups which are reactive with an isocyanate group are hydroxyl terminated polyesters, polyalkylene ether polyols, hydroxyl-terminated polyurethane polymers, polyhydric polythioethers, alkylene oxide adducts of phosphorus-containing acids, polyacetals, aliphatic polyols, aliphatic thiols including alkane, alkene and alkyne thiols having two or more Sl-l groups; diamines including both aromatic, aliphatic and heterocyclic diamines, as well as mixtures thereof. Compounds which contain two or more different groups within the above-defined classes may also be used in accordance with the process of the present invention such as, for example, amino alcohols which contain an amino group and a hydroxyl group. Also, compounds may be used which contain one SH group and one OH group as well as those which contain an amino group and a SH group.

Any suitable hydroxyl-terminated polyester may be used such as are obtained, for example, from polycarboxylic acids and polyhydric alcohols. Any suitable polycarboxylic acid may be used such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassylic acid, thapsic acid, maleic acid, fumaric acid, glutaconic acid, a-hydromuconic acid, B-hydromuconic acid, a-butyl-a-ethyl-glutaric acid, a,B-diethylsuccinic acid, isophthalic acid, terephthalic acid, hemimellitic acid, and l,4-cyclohexane-dicarboxylic acid. Any suitable polyhydric alcohol, including both aliphatic and aromatic, may be used such as ethylene glycol, l,3-propylene glycol, 1,2-propylene glycol, 1,4- butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 1,4-pentanediol, 1,3-pentanediol, 1,6-hexanediol, 1,7-heptanediol, glycerol, 1,1,1- trimethylolpropane, l ,l l -trimethylolethane, hexanel,2,6-triol, a-methyl glucoside, pentaerythritol, and sorbitol. Also included within the term polyhydric alcohol are compounds derived from phenol such as 2,- 2-bis(4-hydroxyphenyl)propane, commonly known as Bisphenol A.

The hydroxyl-terminated polyester may also be a polyester amide such as is obtained by including some amine or amino alcohol in the reactants for the preparation of the polyesters. Thus, polyester amides may be obtained by condensing an amino alcohol such as ethanolamine with the polycarboxylic acids set forth above,

or they may be made using the same components that make up the hydroxyl-terminated polyester with only a portion of the components being a diamine such as ethylenediamine.

Any suitable polyalkylene ether polyol may be used such as the polymerization product of an alkylene oxide or of an alkylene oxide with a polyhydric alcohol. Any suitable polyhydric alcohol may be used such as those disclosed above for use in the preparation of the hydroxylterminated polyesters. Any suitable alkylene oxide may be used such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, and heteric or block copolymers of these oxides. The polyalkylene polyether polyols may be prepared from other starting materials such as tetrahydrofuran and alkylene oxidetetrahydrofuran copolymers; epihalohydrins such as epichlorohydrin; as well as aralkylene oxides such as styrene oxide. The polyalkylene polyether polyols may have either primary or secondary hydroxyl groups and, preferably, are polyethers prepared from alkylene 0xides having from two to six carbon atoms such as polyethylene ether glycols, polypropylene ether glycols, and polybutylene ether glycols. The polyalkylene polyether polyols may be prepared by any known process such as, for example, the process disclosed by Wurtz in 1859 and Encyclopedia Of Chemical Technology, Vol. 7, pp. 257-262, published by lnterscience Publishers, Inc'. (1951) or in U.S. Pat. No. 1,922,459. Alkylene oxide adducts of Mannich condensation products are also useful in the invention.

Alkylene oxide adducts of acids of phosphorus which may be used include those neutral adducts prepared from the alkylene oxides disclosed above for use in the preparation of polyalkylene polyether polyols. Acids of phosphorus which may be used are acids having a P 0 equivalency of from about 72% to about The phosphoric acids are preferred.

Any suitable hydroxyl-terminated polyacetal may be used such as, for example, the reaction product of formaldehyde or other suitable aldehyde with a dihydric alcohol or an alkylene oxide such as those disclosed above.

Any suitable aliphatic thiol including alkane thiols containing at least two SH groups may be used such as 1 ,Z-ethanedithiol, l ,2-propanedithiol, 1,3- propanedithiol, and 1,6-hexanedithiol; alkenethiols such as 2-butene-l,4-dithiol, and alkynethiols such as 3-hexyne-l ,6-dithiol.

Any suitable polyamine may be used including aromatic polyamines such as methylene dianiline, polyarylpolyalkylene polyamine (crude methylene dianiline), p-aminoaniline, l,5-diaminonaphthalene, and 2,4-diaminotoluene; aliphatic polyamines such as ethylenediamine, l ,3propylenediamine; l ,4- butylenediamine, and 1,3-butyle'nediamine, as well as substituted secondary derivatives thereof.

In addition to the above hydroxyl-containing compounds, other compounds which may be employed include graft polyols. These polyols are prepared by the in situ polymerization product of a vinyl monomer in a reactive polyol medium and in the presence of a free radical initiator. The reaction is generally carried out at a temperature ranging from about 40C. to C.

The reactive polyol medium generally has a molecular weight of at least about 500 and a hydroxyl number ranging from about 30 to about 600. The graft polyol has a molecular weight of at least about 1500 and a viscosity of less than 40,000 cps. at 10% polymer concentration.

A more comprehensive discussion of the graft polyols and their method of preparation can be found in US.

ature which, depending on the catalyst, will range from about C. to 50C. Under such conditions almost immediately an exotherm is developed within the reaction system, carbon dioxide is generated and foam forma- 3,304,273; 3,652,639, and in US. 5 tion begins. Alternatively, the foams may be prepared patent application rial N0. 31 1,809 fil d D60- by adding the catalyst to the mixture of polyisocyanate 1972, the diclosures of which are hereby incorporated and a blowing agent. Optionally, a polyol is blended by reference. with the catalyst and added to the mixture of polyisocy- Also, polyols containing ester groups can be emanate and the blowing agent. ployed in the subject invention. These polyols are pre- The present invention also contemplates the incorpared by the reaction of an alkylene oxide with an orporation of additional ingredients in the foam formulaganic dicarboxylic acid anhydride and a compound tion to tailor the properties thereof. Thus, plasticizers, containing a reactive hydrogen atom. A more compresuch as tris( 2-chloroethyl) phosphate; surfactants, such hensive discussion of these polyols and their method of as the silicone surfactants, e.g., alkylpolysiloxanes and preparation can be found in US. Pat. Nos. 3,585,185; polyalkyl siloxanes, may be employed in the invention. 9 541 and 3 39 542, A i clear f the b v Further additional ingredients include auxiliary or supthe particular polyol ingredient employed in the prepaplcmental blowing agents, such as water or halohydroration of the quasiprepolymer is not a critical aspect of carbons, as described in 'p g P pp the present invention, A compound containing at cation Ser. No. 169,526, filed Aug. 5, 1971. Also, inorleast two reactive hydrogen atoms may be so used. game fillers Pigments and the like can be used- In a preferred embodiment of the present invention, any e e the foams P p in accordance herethe condensation of the Organic polyisocyanate is Cap with are rigid cellular products having a density of from ried out in the presence of a polyol. Any of the polyols f one Pound to forty p e P Cubic foot Whieh discussed above in connection with the preparation of exhlblt excellent flame Propemes Such asfire resls' the quasi prepolymers may be employed in the process tance, low smoke evolution and excellent weight retenof the subject invention. Generally from 0.01 to 0.5 equivalent of a polyol having an average functionality polkmfmg Speclfic non'hmmng m e whlch of 2 to 8 and an average hydroxyl equivalent of from are provided to illustrate the enumerated principles deabout 100 to about 3000 will be employed in the pro scr bed herein. All parts are by weight unless otherwise cess of the subject invention. The use of a polyol results mdlcated' In the examples the l e strength in foams of reduced friability without any loss in flame piopemes of the foams were determmed m accorfiance with ASTM-162l, the flame retardant properties by retardancy. If a polyol is employed in the invention, a ASTM D3014 and the friabmt r0 erties b ASTM catalytic amount of a urethane-promoting catalyst may C421 y p p y also be employed. These catalysts are well known in the 5 art and include the metal or organometallic salts of car- EXAMPLES 1 13 boxylic acid and tertiary l f Repreeematiie 9 A series of foams was prepared by simultaneously such compounds are: dibutyltin dilaurate, dibutyltin dladding a co catalyst system to a reaction Vessel acetate, stannous octoate, lead octoate, cobalt naphequipped with a high speed stirrer to which had been e 1 ether f or organemefltalhc salt? f 40 charged a polyisocyanate and in certain cases a surfacboxylic acids in which the metal is bismuth, tlta tant and a blowing agent. An exotherm was generated antimony uramum eadmmm alummum and foam formation followed soon after. Table I, be- 'yi Zine, or nickel as e as other organometalhe low, illustrates thedetails of the preparations. In all Compounds e as a dlselesed I a N cases, infrared spectroscopic analyses indicate that the 2,846,408- Ternary ammes Such as trfethylenedmmme, foams exhibit carbodiimide and isocyanurate linkages. triethylamine, diethyleyelehexlamme, dlmethyle' In Table I the following abbreviations are employed: thanolamine, methylmorpholine, trimethylpiperazine, TD] a mixture f 0/20 by weight 2 4 2,6 to]y]ene N-ethylmorpholine and diethylethanolamine may also dii be employed as well as mixtures of any of the above. PAP! polymethylene polyphenyl isocyanate Preferred urethane-promoting catalysts are the tin salts TD}! 1,3 5- i (N N-di h l i l)h h of carboxylic acids, such as dibutyltin dilaurate and did i i butyltin diacetate. Generally, the amount of the ure- DMP 30 2 4,6- i (di h l i h l l thane-promoting catalyst employed will be from 0.01 DABCO t ieth le di mi part to 10 parts per 100 parts of organic polyisocya- F-] 13 1,1,2-trichloro-1,2,2-trifluoroethane nate. El 18 monofluorotrichloromethane The carbon dioxide-blown foams of the present in- DC-193 -polyalkylsiloxane-polyoxyalkylene copolyvention are prepared by mixing together the organic mer, a foam stabilizer polyisocyanate and the catalyst at an initiating temper- Fur. Alc. furfuryl alcohol TABLE I Isocyanate Blend, Catalyst Blend, pbw. DC- F- F- Cream Rise pbw. Fur. DMP- 193 l 1 B l 13 Time Time Density Example PAPI TDI Alc. TDl-I 30 DABCO pbw. pbw. pbw. sec. sec. pet.

I 100 13.2 1.7 1.0 20 3 55 1.6 2 100 9.8 2.0 1.0 15 3 55 2.1 3 100 9.8 2.0 1.0 2O 31.7 4 100 5.0 8.0 1.0 10 I 520 5.0 5 200 6.0 5.0 2.0 25 6.2

TABLE l-Continued lsocyanate Blend, Catalyst Blend, pbw. DC- F- F- Cream Rise pbw. Fur. DMP- 193 1 1B 1 13 Time Time Density Example PAPI TDI Alc TDH 30 DABCO pbw pbw. pbw. sec. sec. pcf.

EXAMPLES 14-16 15 TABLE 1I-Continued A series of foams was prepared by simultaneously Example adding a co-catalyst system to a reaction vessel Ingredients: 14 15 16 equipped with a high speed stirrer to which had been charged a polyisocyanate and various optional ingredigzi f g' g 14 21 ents such as a polyol, a urethane catalyst, a plasticizer, 2 Content, Corr. 99 100 100 a surfactant and a blowing agent. An exotherm was g z g g Test 88 87 86 0 generated and foam formation followed soon after. Flame gm 7 9 8 Table 11, below, illustrates the details of the prepara- Timcto l0 IO tions as well as physical properties of some of the resulting foams. In all cases, infrared spectroscopic analyses indicate that the foams exhibit carbodiimide, isocyanurate and urethane linkages. In addition to the abbreviations mentioned before, the following abbreviations are employed in Table II: DBTDL dibutyltindilaurate FYROL CEF tris(Z-chloroethyl) phosphate Polyol A propylene oxide adduct of Mannich condensation product of one mole of phenol, diethanolamine and formaldehyde (hydroxyl number of 530) The following examples illustrate the preparation of carbodiimide-isocyanurate foams prepared in the presence of certain polyols. The foams were prepared by mixing at room temperature two streams in a metal container and allowing to foam in 10 X 10 X 4 inch paper boxes. Generally, the mixture foamed in about 2 to 10 seconds and was tack-free in 80-100 seconds. One stream contained the polyisocyanate and blowing agent while the other stream contained the catalysts, surfactant, plasticizer and polyol. Infrared spectro- TABLE II scop1c analyses reveal that foams exhibit carbodiimide,

Example isocyanurate and urethane linkages. Details of the Ingredient? l 4 I 5 l 6 4O preparations as well as physical properties of the result- PAP], mm [00 100 90 ing foams are presented in Table III, below. In addition TDl, pbw. 10 to the ingredients and amounts thereof set forth in the gl i' g g g Table, all foams were prepared employing 9 parts of TDH, pbw. 2.0 2.0 2.0 furfuryl alcohol, 6 parts of l,3,5-tris(N,N-

P35858 pbw dimethylaminopropyl)hexahydrotriazine, 4.5 parts of D0193, pbw, 1,0 tris( 2-chloroethy1) phosphate, 3 parts of dibutyltin diy? A 20 24 24 acetate, and 3 parts of silicone surfactant. Polyol B is Physical Properties:

a 1040 molecular weight polyoxypropylene glycol, gensity 1.9 1.9 1. Polyol C is a 1530 molecular weight propylene oxide g' fi 28 3O 28 5O adduct of glycerol and Polyol D is a 775 molecular Tumbling weight polyoxypropylene glycol.

TABLE 111 Example: 17 I8 19 20 21 22 23 24 25 26 27 28 29 PAPI, pbw. 300 300 300 270 270 270 300 300 300 270 270 270 300 TDI, pbw. 30 30 30 30 30 30 Polyol, pbw. 60B 66B 75B 60B 66B 75B 60C 66C 75C 60C 66C 75C 60D F-l 1B, pbw. 60 60 60 55 55 60 6O 55 55 55 55 Cream time, sec. 12 12 10 11 7 9 10 10 10 10 10 10 14 Rise Time, sec. 30 30 30 25 30 25 25 25 25 25 25 25 45 Tack-free Time, sec. 80 80 80 60 60 70 70 60 60 60 Density, pcf. 1.9 1.9 1.9 1.9 2.0 2.0 1.9 2.0 2.0 2.0 1.9 1.9 2.2 Compressive Strength, psi. 19 21 18 21 16 18 19 20 18 22 18 19 26 Tumbling Friability. %Weight Loss 18 18 16 18 16 18 16 16 12 I6 16 14 30 TABLE III Continued Example: l7 l8 19 20 21 22 23 24 25 26 27 28 29 Closed Cell, Corr.% 97 97 95 97 96 94 99 Butler Chimney Test Weight Ret. 92 93 94 93 96 96 94 93 93 95 95 93 94 Flame Ht m. 5 8 5 7 5 5 7 6 7 6 6 60 Time to sx. sec 10 10 [0 I0 10 10 10 I0 10 I0 10 10 The embodiments of the invention in which an exclul5 4. The process of claim 1 carried out in the presence sive property or privilege is claimed are defined as follows:

l. A process for the preparation of a cellular foam characterized by carbodiimide and isocyanurate linkages which comprises condensing an organic polyisocyanate in the presence of a catalytically sufficient amount of a catalyst system comprising furfuryl alcohol and a tertiary amine trimerization catalyst.

2. The process of claim 1 wherein the organic polyisocyanate is selected from the group consisting of toluene diisocyanate, methylene diphenyl diisocyanate, polyphenyl polymethylene polyisocyanate and mixtures thereof.

3. The process of claim 1 wherein the tertiary amine is l,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine.

of from 0.01 to 0.5 equivalent of a polyol having an average functionality of 2 to 8 and an average hydroxyl equivalent of from about to 3000.

5. The process of claim 4 carried out in thepresence of a catalyst which promotes urethane linkages.

6. The process of claim 5 wherein the catalyst which promotes urethane linkages is dibutyltin diacetate or dibutyltin dilaurate.

7. The process of claim 1 carried out in the presence of a fluorocarbon blowing agent.

8. The process of claim 1 carried out in the presence of tris( 2-chloroethyl) phosphate.

UNITED STATES PATENT OFFICE CETEFICATE 0F CORRECTION PATENT NO. 3,89%,972 DATED July 15, 1975 INVENTOR S Thirumurti L. Narayan and Moses Cenker It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cover page, Inventorm, second line, should read:

"Moses Cenker, Trenton, both of Michigan" Signed and Scaled this fourteenth Day Of October 1975 {SEAL} Attest:

RUTH C. MASON C. MARSHALL DANN 4118511718 ff Commissioner ofPatents and Trademarks 

1. A PROCESS FOR HE PEPARATION OF A CELLULAR FOAM CHARACTERIZED BY CARBONIIMIDE AND ISOCYANURATE LINKAGES WHICH COMPRISES CONDENSING AN ORGANIC POLYISOCYANATE IN THE PRESENCE OF A CATALYTICALLY SUFFICIENT AMOUNT OF A CATALYST SYSTEM COMPRISING FURFURYL ALCOHOL AND A TERTIARY AMINE TRIMERIZATION CATALYST.
 2. The process of claim 1 wherein the organic polyisocyanate is selected from the group consisting of toluene diisocyanate, methylene diphenyl diisocyanate, polyphenyl polymethylene polyisocyanate and mixtures thereof.
 3. The process of claim 1 wherein the tertiary amine is 1,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine.
 4. The process of claim 1 carried out in the presence of from 0.01 to 0.5 equivalent of a polyol having an average functionality of 2 to 8 and an average hydroxyl equivalent of from about 100 to
 3000. 5. The process of claim 4 carried out in the presence of a catalyst which promotes urethane linkages.
 6. The process of claim 5 wherein the catalyst which promotes urethane linkages is dibutyltin diacetate or dibutyltin dilaurate.
 7. The proceSs of claim 1 carried out in the presence of a fluorocarbon blowing agent.
 8. The process of claim 1 carried out in the presence of tris(2-chloroethyl) phosphate. 